Twisted-core brushes are conventionally manufactured by inserting bristles between two branches of a wire that is folded in half, and then by twisting the branches, thereby causing the ends of the bristles to extend in helical layers.
Brushes have been manufactured with a very wide range of bristles for the purpose of benefiting from properties that are satisfactory in terms of taking the composition and of applying it to the eyelashes.
It has thus been proposed to use mixtures of bristles having different stiffness and/or different lengths.
U.S. Pat. No. 4,861,179 describes a mascara brush comprising a mixture of stiff and soft bristles in random manner along the brush.
U.S. Pat. Nos. 5,197,497 and 5,165,760 also describe brushes having mixtures of bristles of different diameters and different lengths.
US application No. 2005/0145262 discloses a manufacturing method that makes it possible to obtain a brush having a substantially uniform mixture of short and long bristles of different diameters.
U.S. Pat. Nos. 5,482,059 and 5,709,230 describe mascara brushes having stiff and soft bristles at two respective end segments, and a mixture of stiff and soft bristles in the intermediate segment.
WO 95/17837 discloses a brush comprising segments having different bristle diameters.